Fuel system

ABSTRACT

A fuel system including fluid logic elements, meters fuel to an internal combustion engine in intermittent pulses of timed duration. The frequency of the pulses is related to engine speed and the time duration of each pulse is related to the instantaneous engine load.

United States Patent 103A,l19,140.2,140.3,140.4,139.l7,139.18;

261/69, 361(Inquired);137/81.5

f I as 42 .V 43

References Cited UNITED STATES PATENTS Drayer .1 Wyczaleck Binder Marks Boothe et al..

Lazar Drayer Morton et a1. Taplin et a1 Primary Examiner-Wendell E. Burns W. Butcher 137/81.5X 137/81.5X 261/361 137/81.5X 137/81.5X 137/81.5X 261/361 137/81.5X l37/81.5

Attorneys-Donald W. Banner, William S. McCurry and John ABSTRACT: A fuel system including fluid logic elements, meters fuel to an internal combustion engine in intermittent pulses of timed duration. The frequency of the pulses is related to engine speed and the time duration of each pulse is related to the instantaneous engine load.

i l I I I I I l l I I l l 221/ I I I l l l 1 I FUEL SYSTEM SUMMARY OF THE INVENTION The present invention relates generally to fuel systems for internal combustion engines and more particularly to a fuel system incorporating fluid logic elements for metering fuel in accordance with engine requirements.

A principal object of the present invention is to provide a fuel system in which fuel is metered to the engine in accordance with engine requirements, a further object is to provide timed injection of fuel. inaccordance with engine speed, and a still further object is to provide injection pulses having a duration corresponding to the instantaneous load on the engine. Other objects and advantages of the invention will become apparent from the following description together with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a fuel system according to the present invention;

FIGS. 20 through 2d are diagrams illustrating various wave shapes occurring in the fuel system shown in FIG. 1;

FIG. 3 is a pictorial representation of a pneumatic signal generator for use in the fuel system;

FIG. 4 is a pictorial representation of a fuel switching device in which pneumatic control pulses are isolated from the fuel passages; and

FIG. 5 is a pictorial representation of an alternate fuel switching device in the form of a pure fluid amplifier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and more particularly to FIG. 1 thereof, the reference character generally indicates a fuel system for an internal combustion engine 11 having an intake manifold 12, air inlet 13 and throttle plate 14. An inlet valve 15 is provided for admitting an air fuel charge to the engine from the manifold 12. At least one fuel nozzle 16 is arranged to deliver fuel to manifold 12 by means of a fluid logic fuelswitching device 19. Fuel under pressure is supplied by pump 18 from fuel tank 17. It is preferable to provide a fuel nozzle 16 and associated circuitry, for each cylinder of the engine, with the nozzle being located near the inlet valve, however, for reasons of simplicity, the following description is generally stated in terms of a single nozzle and the circuitry associated therewith. Where it is desired to use only a single fuel nozzle, it is generally preferable to locate the nozzle in the air inlet 13 for more homogeneous diffusion of the fuel in the air stream.

Fluid fuel-switching device 19 is indicated schematically as a monostable element biased toward bypass leg 21. Ordinarily liquid fuel is delivered to the internal fuel passage 23 of the switching device by means of pump 18 and conduit 22 and is bypassed back to fuel tank 17 by means of bypass leg 21 and conduit 24. Switching device 19 is provided with a pneumatic control passage 26 and a vent passage 27, such that fuel is diverted into delivery leg 28 for delivery to nozzle 16 through conduit 29 in response to a pneumatic control pulse applied to control passage 26. If desired, switching device 19 can be a bistable element connected in an alternate arrangement in which a direct signal is supplied to control passage 26 for delivering fuel to delivery leg 28, while an indirect signal is supplied to passage 27 for bypassing fuel into bypass leg 21.

In the embodiment of FIG. 4, the switching device is designated by the reference character 119 and includes elastic, impervious membrane members 131, 132 connected to each other by a rigid member 133. Liquid fuel is delivered to switching device 119 by means of conduit 122 and ordinarily traverses the internal fuel passages 123, 121 exiting to bypass conduit 124. The diaphragm members 131, 132 are arranged to normally seal fuel passage 123 from fuel delivery leg 128 so that fuel flows exclusively through fuel bypass leg 121 in the absence of a control pulse in control passage 126. When a control pulse is applied to control passage 126, the diaphragms 131, 132 and rigid member 133 are displaced toward the right as viewed in FIG. 4, expelling entrapped air through vent port 127 and communicating fuel delivery leg 128 with fuel supply passage 123 such that fuel is permitted to flow into delivery conduit 129 for delivery to a fuel nozzle such as 16. When the control pulse is absent, the diaphragms 131, 132 and rigid member 133 resume their normal configuration, shown in FIG. 4, excluding fuel from delivery passage 128. The diaphragm 132 provides an impervious interface for isolating the fuel from the pneumatic control signal, while diaphragm 131 provides a similar interface between the fuel and ambient air. If desired, switching device 119 can be modified for bistable operation in which case a direct signal is supplied to control port 126 for initiating fuel delivery, while an indirect signal is supplied to port 127 for terminating fuel delivery to conduit 129.

An alternate embodiment of switching device is shown, in FIG. 5, as a pure fluid amplifier 219 having a fuel supply port 223 supplied by conduit 222. The internal configuration of amplifier 219 is such as to provide a geometric bias favoring bypass fuel passage 221. Therefore, in the absence ofa control signal, fuel ordinarily flows from conduit 222 through supply port 223, and bypass leg 221 to bypass conduit 224. When a control pulse is applied to control passage 226, fuel is diverted into fuel delivery passage 228 according to the principles of fluid amplifier technology. Therefore, when a control pulse is present, fuel flows from conduit 222 through supply port 223, and fuel delivery leg 228 to conduit 2129 for delivery to a fuel nozzle such as 16. t

Referring again to FIG. 1, the circuit for providing the desired pneumatic control pulses will be described in more detail. A source of pneumatic control energy 36 is connected by means of conduits 37, 38, 39, 41 with a pneumatic reference signal generator 42, asignal shaping fluid amplifier 43, and a control-pulse-forming amplifier 44.

Pneumatic reference signal generator 42 has an output conduit 47 connected to control port 46 of amplifier 43, and includes a rotary chopper member connected to the engine 11 by a drive connection 48. The rotary chopper member intermittently interrupts the flow of air from conduit 39 to conduit 47 to provide a pulsating reference signal in control port 46 which has a frequency proportional to engine speed. In a fourcycle engine, it is preferable to drive signal generator 42 from the engine cam shaft, while in a two-cycle engine, it is preferable to take the drive from the drive shaft. In either two- .or four-cycle engines, it is preferable to correlate the signal generator in phase with the operation of the engine inlet valve to provide fuel injection through nozzle 16 while the inlet valve is open.

An example of a reference signal generator is pictorially indicated in FIG. 3 in which the housing 142 includes an inlet port 149, an outlet port 151, and a rotary chopper member 152. As indicated, inlet port 149 is connected to a source 139 of air under pressure, while outlet port is connected to a signal conduit 147. Chopper 152 is connected to a rotary drive member 148 so as to intermittently interrupt the flow of air from conduit 139 to conduit 147, thereby producing a pulsating pneumatic reference signal in conduit 147 which has a frequency proportional to the speed of rotation of drive member 148.

The pulsating reference signal produced by signal generator 42 is fed to control port 46 of amplifier 43. Amplifier 43 is a fluid logic device having alternative output legs 53, 54, biased for delivery to output leg 53. Thus when signal generator 42 interrupts flow to control port 46, output leg 53 is active, alternatively when signal generator 42 permits flow to control port 46, a square wave signal, as indicated in FIG. 2a, is produced in signal leg 54. The function of amplifier 43 is to reform the pulsations from signal generator 42 to produce a crisp reference signal having clearly defined energy levels. As indicated in FIG. 2a, a low frequency square wave 56, 57 is produced during low speed engine operation, and a higher frequency square wave 58, 59, 61 is produced at higher engine speeds. Signal leg 54 thus provides a square wave reference signal, having a frequency proportional to engine speed, to the first control port 62 of pulse-forming control amplifier 44. This signal is also supplied to the signal time delay network which includes the conduits 63. 64, a fluid restrictor 66, and the variable volume pneumatic capacitance chamber 67, connected in series circuit. The time delay circuit is connected to the second control port 68 of pulse forming amplifier 44.

The square wave reference signal, as indicated in FIG. 2a includes a leading edge portion 84 which provides a direct signal to port 62 of amplifier 44. The reference signal is modified in the time delay network, as indicated in FIG. 2b, providing an indirect signal 87 to control port 68 of amplifier 44. The risetime of the leading edge of the delayed signal is substantially proportional to the effective volume of pneumatic capacitance chamber 67. In FIG. 2b, wave form 71 is indicative of small volume-low frequency corresponding to low speed-low load operation of the engine. In a similar fashion, wave form 72 indicates low speed-high load; wave form 73 indicates high speed-low load; and wave forms 74, 76 indicate high speed-high load operation. As shown in FIG. 1, the volume of capacitance chamber 67 is varied by movement of piston 77 therein. Piston 77 is connected to a servomotor 78, 79 which moves in accordance with manifold vacuum by means of the conduit 80. When engine 11 is under light load, piston 77 is moved to a position resulting in small volume in chamber 67. When the load on the engine is increased, piston 77 moves to a position resulting in greater volume in chamber 67. Thus the volume of chamber 67 is varied in accordance with engine load as measured by manifold vacuum.

Pulse-forming control amplifier 44 has a supply port 81 con nected to the source of pneumatic signal energy 36, and includes a bypass leg 82 and control pulse leg 83. Amplifier 44 is biased toward bypass leg 82 such that in the absence of a signal, the signal energy is vented to atmosphere through leg 82. When the engine is operating, a direct signal as indicated by 84 in FIG. 2a is applied to first control port 62, and an indirect delayed signal as indicated by 87 in FIG. 2b is applied to the opposite control port 68.

The effect of the direct signal and the indirect delayed signal is indicated by the algebraic addition shown in FIG. 20. In FIG. the switching levels of control amplifier 44 are indicated by the energy levels S1 and S2. When the signal energy level exceeds S1, the amplifier initiates a control pulse in control leg 83, and when the signal energy level is diminished below $2, the control pulse in control leg 83 is terminated. The operation of control amplifier 44 is illustrated graphically by comparison of FIGS. 20 through 2d. For example, the leading edge 84 of direct signal 56 provides rising portion 86 of the switching signal, while the leading edge 87 of the indirect delayed signal 71 produces the falling portion 88 of the switching signal. When the energy level of rising portion 86 exceeds S1, the control pulse 89 is initiated in control leg 83. In like manner, when the energy level of falling portion 88 drops below $2, the control pulse 89 in control leg 83 is terminated. Control pulse 89 therefore has a time duration which is a function of the difference between direct signal portion 84 and indirect signal portion 87 as determined by the effective volume of capacitance chamber 67. As illustrated in FIG. 2d, control pulse 89 indicates a short fuel injection pulse corresponding to low speed-low load operation. Control pulse indicates a fuel injection pulse of longer duration corresponding to low speed-high load operation of the engine. Control pulse 92 is of short duration indicative of high speedlow load operation, and control pulses 93, 94 are more frequent and of longer duration corresponding to high speed-high load operation of the engine.

Control amplifier 44 thus provides pneumatic control pulses in control leg 83 which have a frequency proportional to engine speed, each pulse having a time duration proportional to the instantaneous engine load as measured by manifold vacuum in the engine. The control pulses thus provided by control amplifier 44 are conducted to fuel switching device 19 by the conduit 96 for application to control passage 26.

Switching device 19 then provides intermittent pulses of fuel to nozzle 16 corresponding in frequency and duration with the controlpulses formed by control amplifier 44. Injection pulses varying in the range of from I to 30 milliseconds are attainable with the described circuitry.

While the foregoing description has been stated in terms of a preferred embodiment of circuitry for metering fuel to a single fuel nozzle, it is to be understood that the principles described can be applied to engines having a plurality of fuel nozzles and that alterations and modifications of the circuitry and elements included therein are comprehended by the described invention. For example, those skilled in the art will readily recognize that the functions performed by fluid logic devices indicated by reference characters 19, 44 in FIG. 1 can be performed by a single element such as switching device 119 in FIG. 4. If desired, switching device 119 may be connected to receive the direct signal in port 126 and the delayed signal in port 127. When connected in this manner, switching device 119 performs the algebraic addition function of element 44 as well as the switching function of element 19.

I claim:

1. A fuel system for an internal combustion engine provided with an intake manifold and inlet valve means comprising:

a source offuel under pressure;

a fuel injection nozzle communicating with said source of fuel and said engine, having pneumatic control means associated therewith for regulating the time duration of fuel injection; and

a pneumatic control circuit connected to said control means, said control circuit including pneumatic reference signal generating means providing a direct signal for initiating fuel injection and pneumatic signal delay means providing an indirect signal for terminating fuel injection; said signal delay means including a variable volume pneumatic capacitance chamber connected to said signal generating means, said capacitance chamber providing a time interval between said direct signal and said indirect signal substantially proportional to the effective volume of said chamber, said control circuit including means for regulating the effective volume of said capacitance chamber in accordance with engine load.

2. A fuel system according to claim 1 including a servomotor communicating with said intake manifold portion of said engine, said capacitance chamber including a movable wall member connected to said servomotor, said servomotor and wall member providing means for varying the effective volume of said chamber in accordance with variations in engine manifold pressure.

3. A fuel system according to claim 1 in which said pneumatic control means includes a fluid logic switching device connected to said source of fuel and to said fuel injection nozzle, said fluid logic device being arranged to deliver fuel to said injection nozzle in response to said direct signal, and to bypass fuel from said injection nozzle in response to said indirect signal.

4. A fuel system according to claim 1 in which said pneumatic control means includes a fluid logic switching device connected to said source of fuel and to said fuel injection, nozzle, said fluid logic device being biased by bypassing fuel from said injection nozzle and including means for selectively switching fuel to said nozzle in response to a pneumatic control pulse, said control circuit including a pulse-forming fluid amplifier having an output leg connected to said switching device and having opposed control ports connected to receive said direct signal and said indirect signal, said fluid amplifier providing a pneumatic control pulse in said output leg having a time duration equal to the time interval between said direct signal and said indirect signal.

5. A fuel system according to claim 1 in which said pneumatic reference signal generating means is connected to said engine providing a reference signal frequency proportional to engine speed in phase with the opening of said inlet valve means.

6. A fuel system according to claim 1 including a servomotor communicating with said intake manifold portion of said engine, said capacitance chamber including a servomot or communicating with said intake manifold portion of said engine, said capacitance chamber including a movable wall member connected to said servomotor, said servomotor and wall member providing means for varying the effective volume of said chamber in accordance with variations in engine UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3 ,556,063 January 19 1971 Patent No. Dated John J. Tuzson Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5 lines 3 to S cancel "a servomotor communicatin with said intake manifold portion of said engine said capitance chamber including".

Signed and sealed this 25th day of May 1971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

1. A fuel system for an internal combustion engine provided with an intake manifold and inlet valve means comprising: a source of fuel under pressure; a fuel injection nozzle communicating with said source of fuel and said engine, having pneumatic control means associated therewith for regulating the time duration of fuel injection; and a pneumatic control circuit connected to said control means, said control circuit including pneumatic reference signal generating means providing a direct signal for initiating fuel injection and pneumatic signal delay means providing an indirect signal for terminating fuel injection; said signal delay means including a variable volume pneumatic capacitance chamber connected to said signal generating means, said capacitance chamber providing a time interval between said direct signal and said indirect signaL substantially proportional to the effective volume of said chamber, said control circuit including means for regulating the effective volume of said capacitance chamber in accordance with engine load.
 2. A fuel system according to claim 1 including a servomotor communicating with said intake manifold portion of said engine, said capacitance chamber including a movable wall member connected to said servomotor, said servomotor and wall member providing means for varying the effective volume of said chamber in accordance with variations in engine manifold pressure.
 3. A fuel system according to claim 1 in which said pneumatic control means includes a fluid logic switching device connected to said source of fuel and to said fuel injection nozzle, said fluid logic device being arranged to deliver fuel to said injection nozzle in response to said direct signal, and to bypass fuel from said injection nozzle in response to said indirect signal.
 4. A fuel system according to claim 1 in which said pneumatic control means includes a fluid logic switching device connected to said source of fuel and to said fuel injection nozzle, said fluid logic device being biased by bypassing fuel from said injection nozzle and including means for selectively switching fuel to said nozzle in response to a pneumatic control pulse, said control circuit including a pulse-forming fluid amplifier having an output leg connected to said switching device and having opposed control ports connected to receive said direct signal and said indirect signal, said fluid amplifier providing a pneumatic control pulse in said output leg having a time duration equal to the time interval between said direct signal and said indirect signal.
 5. A fuel system according to claim 1 in which said pneumatic reference signal generating means is connected to said engine providing a reference signal frequency proportional to engine speed in phase with the opening of said inlet valve means.
 6. A fuel system according to claim 1 including a servomotor communicating with said intake manifold portion of said engine, said capacitance chamber including a servomotor communicating with said intake manifold portion of said engine, said capacitance chamber including a movable wall member connected to said servomotor, said servomotor and wall member providing means for varying the effective volume of said chamber in accordance with variations in engine manifold pressure, said pneumatic reference signal generating means being connected to said engine providing a reference signal frequency proportional to engine speed in phase with the opening of said inlet valve means, said control circuit thereby metering fuel to said engine in accordance with the instantaneous load and speed of said engine. 